Summary
Anthropic released Fable 5.1 and Mythos 5.1 as the same underlying model with different safeguards: Fable is generally available, while Mythos remains restricted to trusted cybersecurity and life-sciences programmes. Anthropic says cache-read pricing makes typical Fable workloads about 25% cheaper and highly agentic workloads up to 45% cheaper, while new safeguards cut cybersecurity false-positive blocks by 60%; customer-controlled Enterprise Frontier Safeguards are planned for later this year.
Why it matters
The release shows frontier labs competing on capability, operating cost and calibrated access controls at the same time, rather than treating safety restrictions as a separate product layer.
Related coverage
- OpenAI says forthcoming Astra crosses its critical cybersecurity threshold
- CrowdStrike and NVIDIA launch SafeMind cyber-defence models
- Aslan launches human-supervised AI undercover agents for national-security missions